er... I think you mean 1tb hdds surely ,A 1GB hdd is not big enough .64bit windows 7 typically takes up 17-18gb initialy ,and will quickly grow well over 20gb once you start installing 3rd party apps .In answer to your question ,yes you can install as many copies as you like onto the same machine ,this does not breach any microsoft rules as the rules state you can only install on a single machine at any one time . and that you must not run more than one copy at a time .neither of these rules apply ,for no matter how many installations you put on your single machine you can only be using one at any one time .so no agreement will have been breached.and there will be no fear of your software becoming blacklisted (the key) as your hardware will be identical for each machine and as a consequence windows update will assume you have only one OS.I use a product called HyperOS ,it will run several copies of any OS (within reason) on the same pc .and will allow you to copy /clone .OSs to other drives and manage and create backups too .

Hi Merlinux, does the cloning mean you can use W7 on another machine without buying another copy...or am I just being hopeful. We have 3 machines that all need some level of upgrade and 3 copies of w7 seems a bit steep

nope ,it means you can install windows7, update drivers /updates etc, and then instead of reinstalling it again to another drive to have 2 copies and have to go through all of the udate/drivers stuff again ,you can simply clone (identical copy ) to another drive . you could then use one for everyday stuff /internet etc. and the other for example could be kept for photo /video editing ,or word processor software .that way if one windows fgoes belly up you can often just boot at start up into the other and do a repair or restore of the damaged one.if you tried to use the same windows 7 cloned or otherwise on other PCs ,during update it would detect different hardware signitures and all of you installs using the same product activation key would become deactivated and you will be notified.

Anyway, thank you for your kind reply which confirms what I thought. I'm just really curious to see whether or not there will be any significant gain in performance between the upgrade I am currently using and a clean install. The upgrade, performed as soon as Win 7 arrived on the scene, has been faultless - no crashes, never failed to boot, boringly reliable really. Runs my photo and video editing programmes, flight simulators and anything else I throw at it without any trouble.

I use an AMD Phenom x4 965 Black edition, 8GB DDR2 RAM and a Radeon 4890 Graphics card. Not the world's fastest computer by a long way, but solid and reliable.